Uploaded devices sometimes not in devmap (race condition)

[eaton-coreymutter]

🐞 Bug Report

Affected Services [REQUIRED]

The issue is located in: device-sdk-c

Is this a regression?

Yes, the previous version in which this bug was not present was: ....

Description and Minimal Reproduction [REQUIRED]

We have seen some instances where an uploaded device (e.g. res/devices/xxx.yaml) gets created and exists in core-metadata, but is not in the service's devmap, so resource operations return 404 until the service is restarted.

This seems to be a race in service.c startConfigured() where we call edgex_bus_register_handler() to get the callback to edgex_callback_add_devices(), which is the function that actually adds to the devmap. Then we immediately call edgex_device_devices_upload(), but in bus-mqtt.c we are calling an async subscribe function and it has apparently not finished, so we miss the callback because core-metadata posts the system event before our subscription has taken effect.

🔥 Exception or Error

🌍 Your Environment

Deployment Environment: Yocto, MQTT message bus

EdgeX Version [REQUIRED]: Post-3.1 main branch

Anything else relevant?

Posting a PR with the fix that worked for us - have edgex_bus_mqtt_subscribe() not return until that async subscribe is complete, by calling MQTTAsync_waitForCompletion().

It has been getting lots of exercise in our automated system test framework with no apparent ill effects,